The present invention relates to the stopping of objects such as semiconductor wafers that are being transported along a track on an air film. In particular it relates to a method and mechanism for stopping and holding an object at a particular point along the track.
Co-pending U.S. patent application Ser. No. 754,306, filed on Dec. 27, 1976, assigned to the same assignee as this invention and entitled, "Wafer Air Film Transportation System" now U.S. Pat. No. 4,081,201 discloses a track configuration in which the air film supporting objects such as semiconductor wafers being moved along the track is controlled by the configuration of the track to eliminate the need of a wafer guide or restraint to keep the wafers on the track. In such systems it is not only desirable to transport the wafer, it is also necessary at times for the wafer to be stopped, reoriented and/or redirected. Again when these functions are being performed, it is desirable that the wafer not be contacted to any great extent by solid objects since such contacting of the wafer may cause damage to the circuits on the wafer resulting in lower yield rates of good circuits on the wafer. Therefore there is a need for a mechanism that will stop, hold, orient and change directions of wafers traveling along a track on an air film with a minimum of physical contact to the wafer by solid objects.